This application claims the priority benefit of Taiwan application Ser. no. 90125886, filed on Oct. 19, 2001.
1. Field of Invention
The present invention relates to a structure of a gene gun. More particularly, the present invention relates to the contour design of the spray nozzle of the gene gun, which would modify the gene gun operation, wherein gene transformation is accomplished with nitrogen gas and only low pressure, obviating damages to cells and the problem of noise.
2. Description of Related Art
Gene delivery system has been widely used in gene therapy and optimizing the genetic make-up in plant material. The current gene transformation method includes using a physical method for gene transformation, such as the development by Klein (1987) for more than ten years on particle gun and its application in gene transfer and gene transformation. The technique of particle gun is first applied in the research and development of plant materials since this technique can effectively overcome the barrier of plant cell wall. Particle gun is also applicable to the research and development of other fields, for example, gene therapy of mammalian cells and hormone cells, and the recently developed DNA vaccination.
The earlier devised particle gun system uses a gas to pressurize a gas acceleration tube. When a preset high pressure is reached in the pressurized chamber, a DNA/RNA particle-coated thin film is accelerated by a resulting shock wave into a stopping screen. The DNA/RNA particles continue to accelerate to enter the target tissue due to the inertia effect. The gas that is used to create the high pressure in the pressurized chamber varies and is normally maintained at a pressure of about 1000 lb/sq. in. (PSI).
The particle gun technique has improved tremendously in the recent years. The DNA/RNA-coated microcarriers are coated on the inside wall of a sample cartridge. The microcarriers accelerate for maximum penetration into the target based on the high pressure shock wave principle (Henning et al., 1999). A major disadvantage of the aforementioned methods is the loud noise resulting from the shock wave. The high speed and high pressure gas that is generated by the shock wave also causes cell deaths. Moreover, the gas used in the conventional particle gun technique employs the expensive helium gas.
According to the theory of aerodynamic, a supersonic flow is generated when the pressure difference between the inside and the outside pressures of the nozzle is greater than 1.9 atm. Further based on the bi-phase flow theory, a high speed air flow can carry the particles that are few centimeters apart in the air from a stationary state to accelerate to an extreme high speed. Based on these two theories, the present invention provides a low-pressure gene gun, wherein the problems of low noise, cell death induced by shock wave and the application of the expensive helium gas are prevented.
To resolve the aforementioned problems, the present invention provides a gene gun, which is operable under a low pressure, using a nitrogen gas or a helium gas to directly accelerate the micro-carriers, such as gold or tungsten particles, to an extreme high speed, for example, greater than 200 m/sec. The micro-carriers, on which the surface is coated with nucleic acid of a foreign gene, penetrate through the cell membrane of animal or plant epidermal cells and enter into cytoplasma or the cell nucleus to express the special protein and to generate the new biological function.
The present invention provides a gene gun, wherein the gene gun is applicable in gene transformation. According to a preferred embodiment of the present invention, the contour design of the spray nozzle of the gene gun allows a modification of the gene gun operation to operate at a much lower pressure. A gas travelling at supersonic speed is used to accelerate the micro-carrier from a stationary state to an extreme high speed, penetrating the epidermis and entering the cell.
Since a low pressure is used, particles are driven into the cell to achieve gene transformation with minimal noise and damages to the cells. Moreover, the conventional gene gun requires a helium gas source, whereas a nitrogen gas is also acceptable for the present invention. Depending on the situation, a selection between a nitrogen gas source and a helium gas source is provided by the present invention.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.